The limited availability of donor hearts for people with end stage heart failure has driven the continual development of ventricular assist devices (VAD) and total artificial hearts (TAH). These can be broadly classified into pulsatile and continuous flow systems. Pulsatile systems drive blood indirectly through blood pumps, resulting in minimal blood trauma. The disadvantage of these systems, however, is their relatively large size. Continuous flow systems offer smaller size and simplicity, but with a flow driver that directly contacts blood, resulting in an increased tendency toward thrombosis and hemolysis. The TAH described here can potentially combine the blood compatibility of a pulsatile TAH with much of the simplicity and smaller size of continuous VADs. The proposed device modifies our existing electrohydraulic TAH by using a continuously rotating valve (CRV) to shuttle hydraulic fluid between left and right blood pump actuation. The CRV eliminates any mechanically oscillatory part such that all parts are in continuous circular motion thus extending the device reliability. The device operates as a simpler low stroke volume, high beat rate pump, which can deliver up to 7 L/min against a l00 mmHg afterload, and has the potential to be 1/2 the size of the existing pulsatile systems. Phase I studies demonstrated the transition from pulsatile to near-continuous flow with a physiological load, as well as a preliminary in vivo demonstration of the device performance. Phase II studies will focus on miniaturization of the device down to a total volume of 400 cc, and further in-vivo characterization, including studies of nonpulsatile versus pulsatile circulatory support using the same device. PROPOSED COMMERCIAL APPLICATIONS: The potential application will be to the more than 100,000 people who die of heart failure annually. Commercial applications of the device being developed will expand from those currently envisioned for exists VASs and TAHs principally because of the increased simplicity and decreased size, without compromise in blood compatibility.